I recently purchased a 1.2 8x8 yellow matrix from Adafruit, along with a HT16K33 backpack for it. I joined the matrix and the backpack, connected everything to the arduino, followed the instructions on the site and got it to work. During animation certain rows would not light up and upon later examination I realized that I had to solder up the pins to the backpack because some pins would not completely make contact with the backpack. After soldering the matrix to the backpack, I fired up arduino and uploaded the matrix8x8 sketch that comes with the library to test the matrix and nothing happens.
I don't have a multimeter yet, but tried to check whether electricity is reaching the backpack which turns out to be true. (used a led and connected it to both + and -, and data and clock pins on the backpack.) in both cases the led lights up.
How can I check the health of the backpack and/or matrix?